A system for direct scanning of gel chromatography columns has been designed and constructed. It runs in response to a SYM-1 microprocessor which is in turn controlled by a PDP1104 minicomputer. This system will be applied to the study of a number of enzymes. Active enzyme chromatography will be done with yeast hexokinase to examine the effects of ATP analogs and lyxose on the association-dissociation properties of the enzyme. Methods for computer simulation of mass transport of associating systems will be applied to the data to obtain quantitative estimates of the association constants for the hexokinase dimerization. Active enzyme chromatography will also be applied to the interaction of nitrogenase components from wild-type and mutant forms. By monitoring dithionite oxidation it will be possible to examine the association of the protein components during the turnover of the enzyme. When combinted with simulation of the mass transport, association constants and stoichiometries of interaction can be derived.